How electoral reform would have changed the result

Labour and the Lib Dems would have a majority under a different voting system.

Interest in electoral reform appears to be at an all-time high (I never thought I'd see "proportional representation" trending on Twitter), but how would Friday's result look if we'd already abandoned first-past-the-post?

First-past-the-post

Above is the result as it stands. The Tories won 36 per cent of the vote and 47 per cent of the seats, Labour won 29 per cent of the vote and 40 per cent of the seats and the Lib Dems won 23 per cent of the vote but just 9 per cent of the seats.

Single Transferable Vote

But if we rerun the election under the Single Transferable Vote (STV), the proportional system favoured by the Lib Dems, a very different picture emerges. The Tories fall 60 seats to 246, while Labour falls 51 seats to 207. Meanwhile, the Lib Dems gain no fewer than 105 seats and rise to 162.

The Electoral Reform Society used data from a recent ComRes poll to work out where people's second-preference votes would go.

It's worth noting that under STV, Labour and the Lib Dems hold 369 seats between them, well over the 326 needed for a parliamentary majority. Had Labour abandoned its conservative instincts and opted for proportional representation, the chance of a coalition with Nick Clegg's party would now be much higher.

The Alternative Vote

But if we rerun the election under the alternative vote, which is not a proportional system, the result is far less striking. Labour goes up four seats to 262, the Tories fall 25 seats to 281 and the Lib Dems rise 22 seats to 79.

Still, it's worth noting that in this scenario Labour and the Lib Dems again easily pass the 326-seat threshold, with 341 seats between them. Thus, even moderate electoral reform would significantly improve the chance of a "progressive coalition" in the future.

If, as now looks likely, the Lib Dems reach an agreement with the Conservatives, we can expect many accusations of betrayal. But it is worth remembering, looking at these figures, that it was Labour, made arrogant by its landslide victories, that betrayed the Lib Dems on electoral reform.